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    <title>位置3 外部样式</title>
    <link rel="stylesheet" href="position3.css">
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<body>
    <h1>欢迎来到尚硅谷学习</h1>
    <h2>这是二级标题</h2>
    <img src="a.jpg" alt="侧视图">
</body>
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